It's almost absurd how many things this one tiny app can do. Some of it is just mind boggling (I can't imagine a situation in which I'll ever need to look up planetary weight), but it does bundle tons of useful little utiltiies into one app, so you can delete comparable unitaskers from your home screen. Just a few of the useful features include:

Dictionary, thesaurus, and sample word usage

Google Translate

Music artist info, find similar artists, and grab album art

Sales tax calculator

Tip calculator

Unit conversions

Actor, actress, and film lookup

Phone memory usage

URL shortener

Holiday lookup

Just hit Menu > More > Extras to try any of these out. Once it finds the information you're looking for, you can save that as a note in your notebook, which is really nice. Plus, you can save any of your notes to Dropbox and Google Docs, share notes through Facebook or Twitter, add events to Google Calendar, and more. Hit the link to gawk at the full list of features.